During the last few decades, political campaigns appear to have become increasingly professionalised. However, at present most of the evidence for the professionalisation of political campaigning comes from countries such as the United States and Britain, and there is less evidence with regard to countries with party-centred systems, proportional elections and multiple parties. Moreover, there is a noticeable lack of systematic and comparative research on the extent to which political campaigns have become professionalised. At present, the only theory of professionalised campaigning that has been operationalised to allow systematic comparisons is the party-centred theory of professionalised campaigning. However, so far it has only been applied once. Thus the usefulness and validity of the theory remains largely unclear. Against this background, the purpose of this study is to elaborate on the party-centred theory of professionalised campaigning, and to test this theory in the context of the 2006 Swedish election.